Acid-producing bacteria comprise a relatively diverse group of Gram positive microorganisms that share common metabolic and physiological characteristics. This group of bacteria produces acid as the major end product of the fermentation of carbohydrates. The group is divided into two metabolic subgroups—homolactic fermenters, which convert carbohydrates essentially into acid; and heterolactic fermenters which, in addition to producing acid, also convert carbohydrates into other metabolites including ethanol and carbon dioxide, for example.
Although some acid-producing bacteria, such as lactic acid-producing bacteria (LAB) have a beneficial role in the production of fermented foods, they also are known as a principal agent of food and beverage spoilage, particularly in vacuum-packaged meats, meat products, and beer. The metabolic activity of acid-producing bacteria in certain food products can lead to significant deterioration of the organoleptic properties (e.g., smell, taste) of the food or beverage.
Traditional microbiological techniques are typically used to identify and/or enumerate acid-producing bacteria, such as LAB. Agar and broth culture media (e.g., MRS and APT media) are used to promote growth and/or identify acid-producing bacteria. The cultures are incubated in microaerophilic environments to improve the growth of the acid-producing bacteria, such as LAB. Typical methods include the growth and isolation of presumptive acid-producing bacteria colonies on a selective agar plate, followed by subculture in a broth medium containing a fermentation tube to detect the production of gas by heterolactic fermenting species. These methods may take up to four days to detect or identify the acid-producing bacteria. In some cases, the methods may take from 7-10 days to identify the acid-producing bacteria.
There exists a need for simple articles and methods for the detection of acid-producing bacteria, such as LAB, in a sample.